The first annotated storm in central Oregon only had weak satellite growth, but the ProbSevere value ramped up quickly an account of increasing MESH and the total lightning flash rate, in a very high shear environment. A brief tornado was reported at 20:22 UTC (probability > 90%) while golfball-sized hail was reported at 20:30 UTC.
Two other annotated storms in northern Idaho and far northeastern Oregon also had high probabilities. On both of these storms, the normalized satellite growth rate and glaciation rate were strong before the MESH became high, yielding 80%+ probabilities of severe. The flash rate also remained rather low until later in the lifecycle of the storms. The storm in Idaho had a report of 1" hail at 21:24 UTC, and later 2" hail at 21:45 UTC (a severe thunderstorm warning was issued at 21:12 UTC). The storm traveling from northeast Oregon to far southeast Washington report damaging 1.25" hail at 21:45 UTC (the hail dented vehicles).
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| Fig. 1: The OR-WA-ID tristate region, with ProbSevere contours, composite reflectivity, and NWS warnings. |
On June 13th, a slow-moving storm brought hail to the Salt Lake City, Utah area in the early afternoon. Very strong satellite growth rates were observed at 17:45 UTC in an environment characterized by 1500 J/kg of MUCAPE and 25 kts of effective shear. A total flash rate of about 30 flashes/min and MESH close to 1" yielded a maximum probability of severe of 88% at 18:14 UTC. One-inch hail was reported at 18:20 UTC, and golfball-sized hail reported at 18:37 UTC.
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| Fig. 2: Storm near Salt Lake City, UT produces multiple large hail reports. ProbSevere contours are overlaid NWS warnings and composite reflectivity. |